The invention concerns a tool for the cutting of workpieces, especially by rotary drilling.
Tools of this type are known (e.g., see DE-OS No. 14 02 911) wherein the cutting blade carrying out the operation is located eccentrically relative to a rotating axle of the drill chuck. The chuck is rotated and advanced relative to the workpiece to roughly cut a hole. Thereafter, the chuck is retracted through the roughly cut hole to make a finishing cut. The eccentric is pressed by a spring against a stop, against which it is abutting during the advance movement of the drilling tool during the roughing cut. Movement of the eccentric against the stop is effected initially by the spring and then during a roughing cut by the torque acting additionally on the eccentric. When the roughing cut is completed, the eccentric may be rotated against the bias of the spring by means of an adjusting spindle guided in the drill chuck, whereby the cutting edge is displaced to revolve at a larger diameter around the axle of the drill chuck. During the subsequent retraction of the drilling tool through the roughly cut hole, a finish cut may be effected with that larger diameter, while the formation of a helical groove in the finished borehole by an edge of the cutting blade is prevented.
In other prior art cutters (DE-OS No. 27 15 234) it is known to reposition the cutting edge of a drilling tool after the completion of the initial cut into a radial retracted position in which no contact of the cutting edge with the finished internal surface of the bore is possible during the retraction of the drill through the hole. However, in order to make a finishing cut the tool must be reset and re-advanced through the bore. This is expensive.
It is an object of the invention to provide a cutting tool for peripheral cutting machining of the aforementioned type, so that both the advance and return motions of the tool may be used for cutting, but without the need for a mechanical or powered adjusting device for changing the blade cutting diameter.